Studies are progressing on four different proteins or enzyme systems: 1. Lactose synthetase, which is the enzyme responsible for the ultimate synthesis of milk lactose in the mammary glands. Considerable insight has been obtained into the structure of the two protein components of lactose synthetase and how they interact in the mammary gland to effect biosynthesis of lactose. 2. Superoxide Dismutase. This enzyme, which serves the biological role to prevent the toxic effects of oxygen in all aerobic species, including man, is being investigated. The complete amino acid sequence of the copper-zinc enzyme from bovine erythrocytes has been established and the mangenese containing enzyme of bacteria and mammolian mitochondria is now being studied in detail and a complete sequence will be forthcoming. 3. Blood Clotting Proteins. The nature of the conversion of fibrinogen to fibrin as well as the crosslinking of fibrin by Factor XIII is being investigated structurally. The mechanism of plasminogen activation is also being examined and the effects of plasmin, a proteolytic enzyme which dissolves blood clots, is being examined with respect to its action on fibrin. 4. The glycosyl transferases involved in the biosynthesis of procine mucin are being isolated and examined structurally and kinetically.